#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
	int n,t,m[99],i,j,v[99],vq[99],temp,now=0,tv,tq;
	float value=0;//value/quality
	cin>>n>>t;
	for(i=0;i<n;i++)
	{
		cin>>m[i]>>v[i];
		vq[i]=v[i]/m[i];
	}
	for(i=0;i<n-1;i++)
	{
		for(j=i;j<n-1;j++)
		{
			if(vq[j]<vq[j+1])
			{
				temp=vq[j];tv=v[j];tq=m[j];
				vq[j]=vq[j+1];v[j]=v[j+1];m[j]=m[j+1];
				vq[j+1]=temp;v[j+1]=tv;m[j+1]=tq;
			}
		}
	}
	i=0;
	while(now<t)
	{
		now+=m[i];
		value+=m[i]*vq[i];
		i++;
	}
	value=value-(m[i-1]*vq[i-1])+(t+m[i-1]-now)*vq[i-1];
	printf("%.2f",value);
}